Infant stumptail macaque monkeys will be studied for brain and behavioral effects of somatosensory and sensory-motor deprivation. Three restricted rearing and one control condition will be used. At 3 and at 6 months comparisons will be made across rearing conditions for differences in dendritic growth. These differences will be correlated with behavioral differences. Sensory and motor areas of the cerebral cortex and the various cellular layers of the cerebellum will be studied layer by layer to determine changes related to age and to rearing conditions. Visual and prefrontal cortex will be studied as possible control areas to discover whether alterations in cell structures are specific or general to various cortical areas. A comparison group of infants will be deprived for the first 3 months and returned to our social rearing condition for a study of recovery. This has proved to be feasible with our highly stable social group. Deviant social behavior is well tolerated.